Dear Hafiz,
Yes allow 0365 application instead of IP/url. IP/URL of 0365 will keep on changing better to use application.
You can use this cpl too.
<proxy>
condition=O365-Applications authenticate(no) detect_protocol (none) allow
define condition O365-Applications
request.application.name="Lync Online"
request.application.name="Office 365 Exchange"
request.application.name="Office 365 Sharepoint"
request.application.name="Office Online"
request.application.name="Windows Live SkyDrive"
request.application.name="Yammer"
end condition O365-Applications